Magneto-rheological clutch assemblies are used to transfer torque from an input member to an output member. These clutches use a magneto-rheological fluid in combination with excitation coils to control the speed of a rotating member. An example of such a clutch assembly is shown in U.S. Pat. No. 5,598,908.
One disadvantage of using magneto-rheological clutches in earthmoving machines is the high input torque and input speeds that are supplied to the clutch. In an application such as an agricultural tractor power-take-off (PTO), the engine and transmission can supply high torque to a clutch assembly. The magneto-rheological fluid has a centrifugal load limit which can be exceeded if clutch members are rotating too fast.
Typically, a power-take-off (PTO) is driven by the clutch assembly to run other agricultural machinery. Often, the other machinery does not require high torque input to run the machinery. If the machinery experiences a problem, the clutch can overload the machinery by exceeding the torque limit of the machinery. This can cause irreparable damage to the machinery.
Thus, it is desirable to have a magneto-rheological clutch that can operate at higher torque outputs while having the capability to operate at lower torque loads during certain applications.
The present invention is directed to overcoming one or more of the problems as set forth above.